VARIABILITY OF 13 ISOZYME LOCI IN THE USDA SOYBEAN GERMPLASM COLLECTIONS

Surveys of variability at loci that condition simply inherited, phenot ypically neutral characters can be used to investigate relationships a mong accessions in germplasm collections. We performed a survey of iso zyme variability among 1005 domesticated soybean [Glycine max (L.) Mer r.] and 258 wild soybean [G. soja (L.) Siebold and Zucc.] accessions f rom the USDA soybean germplasm collection. By using eight activity sta ins, we detected polymorphisms conditioned by 13 isozyme loci. The ave rage gene diversity of the Asian G. max accessions in this study was 0 .198, while that of the G. soja accessions was 0.235. The relatively h igh variability of this set of loci made it possible to investigate re lationships among groups of accessions from six diverse geographic reg ions in Asia: China, India and South-Central Asia, Japan, Korea, Manch uria-Siberia, and Southeast Asia. The G. max and G. soja accessions fe ll into two separate groups, based both on genetic distance and canoni cal discriminant analysis. Publicly developed soybean cultivars releas ed for production in North America clustered with the G. max accession s from northeast Asia. The group of accessions from India and South-Ce ntral Asia was the G. max group most closely related to the G. soja ac cessions and may include some primitive agronomic types. The group of G. max accessions from Southeast Asia stood out from the other G. max groups. This difference was due to high frequencies of the Aco3-b, Dia l, and Enp-a alleles among accessions in Maturity Groups VII through X . The accessions in the later maturity groups may represent a distinct population, relative to the accessions in the earlier maturity groups .